Crontab: Difference between revisions
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Revision as of 00:58, 3 November 2011
Crontab is the equivelant of the scheduler in Windows.
Crontab Commands
crontab -e | Edit your crontab file, or create one if it doesn't already exist. | ||
crontab -l | Display your crontab file. | ||
crontab -r | Remove your crontab file. | ||
crontab -v | Display the last time you edited your crontab file. |
Crontab File
A crontab file has five fields for specifying day , date and time followed by the command to be run at that interval.
* * * * * command to be executed - - - - - | | | | | | | | | +----- day of week (0 - 6) (Sunday=0) | | | +------- month (1 - 12) | | +--------- day of month (1 - 31) | +----------- hour (0 - 23) +------------- min (0 - 59)
Example
of Specific Minutes
3,5,10-15,30,55-60 * * * * /command/to/run.sh
of every 4 hours
* */4 * * * /command/to/run.sh
at boot
To run a file at boot only enter the command to run with no minute, hour, day, month or day of week paramaters.
Disable Email Notifications
By default cron jobs sends a email to the user account executing the cronjob. If this is not needed put the following command At the end of the cron job line .
>/dev/null 2>&1